In accordance with the diffusion of applications, such as the Desk Top Publishing system, the Document Formatting system and the Document Editing system, it is easy to make a document by using a computer. However, as for allocating the diagrams(figures and tables), there are few document processing systems able to allocate diagrams on the appropriate places automatically. In a document processing system it is a very important issue to allocate diagrams on the most suitable places. This paper defines the criteria for allocating diagrams on the suitable positions by investigating published papers. These criteria concern 1) the order of diagrams to be allocated, 2) the stability of the diagram allocations, 3) the distance between the diagram and the location of the corresponding first reference in the text, 4) the allocation balance of diagrams in a text, 5) the restricted areas where diagrams shouldn't be allocated, 6) the allocation priorities between diagrams of different width. Moreover, this paper proposes a method for deciding the diagram allocations satisfying the above criteria automatically and fast on document formatting systems. In this case we have limited its application to one type of documents, which is papers. Especially, this method can skillfully allocate diagrams of different width on the page by reallocating the diagrams and texts within it, and can allocate diagrams over the document uniformly. But, this method doesn't have to reallocate diagrams, which have been already allocated, beyond the page. From the experimental results using various published papers (50 papers including 556 diagrams), 94.7 percent of the diagrams in these published papers satisfy the criteria defined in this paper, and so we confirmed the validity of the criteria. And, it has been shown that, by using this method, 99.8 percent of the diagrams satisfy the criteria. Furthermore, it has been shown that 82 percent of diagrams are allocated on the same place and 98 percent on the same page of the published paper. As for the execution time of the proposed method, it takes less than 1 second.